Advertisement

Advertisement

New Scientist Live

The incredible naked mole rat can survive with hardly any oxygen

Can last 18 minutes in pure nitrogen

Roland Gockel / MDC

By Michael Le Page

THE naked mole rat can cope fine with oxygen levels low enough to kill us. It can even go 18 minutes with no oxygen at all.

To investigate how well these East African rodents tolerate low oxygen, a team of biologists put them in a chamber with just 5 per cent oxygen, less than a quarter the amount found in air. Such conditions kill mice within 15 minutes – and we wouldn’t survive either.

But naked mole rats just carry on as normal. The first test was stopped after 5 hours when nothing happened, says Thomas Park at the University of Illinois at Chicago. “We were blown away.”

Advertisement

Next, mole rats were put in pure nitrogen. Being without oxygen kills mice in about a minute. People pass out after a breath or two of pure nitrogen, and would probably die in under 10 minutes. But the mole rats survived for at least 18 minutes. They stopped breathing after a few minutes, but their hearts kept beating and they revived as soon as they were returned to normal air. “They come back to life without any apparent problems,” says team member Gary Lewin of the Max Delbrück Center for Molecular Medicine in Berlin, Germany.

Diving mammals such as whales can hold their breath for over an hour. But between dives they breathe air at the surface and store oxygen in their tissues to help them survive.

Naked mole rats, by contrast, live in underground colonies of up to 300 animals where oxygen is likely to be limited. “They live in really challenging conditions,” says Chris Faulkes of Queen Mary, University of London.

The tunnels that link colonies to the surface are narrow and can get blocked by heavy rain, he says. What’s more, the animals tend to huddle in nesting chambers. “They like to pile together in a big heap of naked mole rats,” he says.

So how do they cope with the resulting lack of oxygen? Partly by minimising their need for it. Naked mole rats have a low metabolism and burn little energy heating their bodies, instead staying at the same temperature as their burrows – around 30°C.

They also go into a sort of suspended animation in zero oxygen. But the team found a clever metabolic trick that helps the mole rats survive, too.

Animal cells get their energy from “burning” glucose. When there is no oxygen, these cells must use far more glucose to get the same amount of energy, and the process produces lactic acid. High lactic acid levels can kill cells, so a feedback system soon kicks in to shut down the process, says team member Jane Reznick, also at the Max Delbrück Center.

But if cells use the sugar fructose instead, they can bypass this system and keep producing energy. And that’s exactly what naked mole rats do: they release fructose into their bloodstream when oxygen drops too low. The sugar is taken up by heart and brain cells to keep critical systems running (Science, doi.org/b53c).

This article appeared in print under the headline “This rat survives with little oxygen”